The speed of scanning in a probe microscope can be increased by operating two or more cantilevers in parallel, such that data is acquired simultaneously from each probe. Parallel operation in scanning probe microscopy (SPM) is a challenge because multiple probe detection must be implemented as well as independent actuation systems for each cantilever. As a result, parallel SPM systems have in the past differed significantly from conventional SPM systems. For example, some systems have deployed cantilevers with integrated piezo-resistive sensors, and integrated zinc oxide Z-actuators (Quate et al Applied Physics Letters vol 67 No 26 3918 (1995)). A major difficulty with such integrated systems is the complexity and corresponding cost of the sensors. The designs are also inflexible since changing a simple parameter such as the pitch or spring constant of the cantilevers also requires a redesign of the layout and costly fabrication. As a result, parallel SPM systems of this sort have not been widely used. There is therefore a need for a parallel probe microscope that is flexible in operation and configuration. Furthermore, such a system should incorporate a probe detection system and a probe actuation system that have at least the performance of conventional SPM, while retaining compatibility with cantilever probes widely used in SPM.
Conventional probe microscopes employ piezo-electric elements to scan the cantilever or specimen with nanometer level accuracy or better. However, such piezo-elements often have a limited speed of response due to their size and mechanical characteristics. Smaller elements which can be integrated into the cantilever can be employed for fast scanning applications but the required fabrication and electrical connection is a challenge. Photothermal actuation has therefore been developed, in which an infra-red laser is focused onto a cantilever and used to induce photothermal bending of the cantilever for both z-actuation and resonant excitation (Yamashita et al, Rev. Sci. Instrum. Vol 78, 083702 (2007). This approach is powerful and flexible, and can achieve a rapid response time due to the small size and short thermal time constant of the micromechanical cantilever. However this approach has not been used for multiple probe control due to the increased number of optical components needed for alignment and focusing.